023：Fun和Do

(21条消息) 023:Fun和Do_Simon_Paul的博客-CSDN博客

 1 #include <iostream> 
 2 using namespace std;
 3 class A { 
 4     private: 
 5     int nVal; 
 6     public: 
 7     void Fun() 
 8     { cout << "A::Fun" << endl; }; 
 9     void Do() 
10     { cout << "A::Do" << endl; } 
11 }; 
12 class B:public A { 
13     public: 
14     virtual void Do() 
15     { cout << "B::Do" << endl;} 
16 }; 
17 class C:public B { 
18     public: 
19     void Do( ) 
20     { cout <<"C::Do"<<endl; } 
21     void Fun() 
22     { cout << "C::Fun" << endl; } 
23 }; 
24 void Call(
25 // 在此处补充你的代码
26 B& p
27 ) { 
28     p.Fun(); p.Do(); 
29 } 
30 int main() { 
31     C c; 
32     Call( c); 
33     return 0;
34 }

如果B不是派生而来且没有fun函数，那么会报错。除非B里有fun函数且为虚函数，p才会调用C里面的fun函数

 1 #include <iostream> 
 2 using namespace std;
 3 /*class A { 
 4     private: 
 5     int nVal; 
 6     public: 
 7     void Fun() 
 8     { cout << "A::Fun" << endl; }; 
 9     void Do() 
10     { cout << "A::Do" << endl; } 
11 }; */
12 class B/*:public A*/{ 
13     public: 
14     virtual void Do() 
15     { cout << "B::Do" << endl;} 
16 }; 
17 class C:public B { 
18     public: 
19     void Do( ) 
20     { cout <<"C::Do"<<endl; } 
21     void Fun() 
22     { cout << "C::Fun" << endl; } 
23 }; 
24 void Call(
25 // 在此处补充你的代码
26 B& p
27 ) { 
28     p.Fun(); p.Do(); 
29 } 
30 int main() { 
31     C c; 
32     Call( c); 
33     return 0;
34 }

报错截图：